1. Field of the Invention
The invention relates to a vehicle bumper beam and, more particularly, to an underrun prevention member that prevents occurrence of a situation where a bumper beam underruns a collision object or the collision object underruns the bumper beam to damage a vehicle component, such as a radiator.
2. Description of the Related Art
A bumper beam (also called bumper reinforcement) is widely used. The bumper beam is disposed at the front portion or the rear portion of a vehicle so as to extend substantially horizontally in a vehicle widthwise direction. The bumper beam may underrun a collision object or a collision object may underrun the bumper beam to damage a vehicle component, such as a radiator. To prevent occurrence of this situation, a technology, in which an underrun prevention member that protrudes upward or downward beyond a bumper beam is integrally fixed to the bumper beam, has been devised. A device described in Japanese Patent Application Publication No. 2009-1199 (JP-A-2009-1199) is an example of the underrun prevention member. The underrun prevention member includes (a) a bottom wall that is fixed to an upper portion of a bumper beam; (b) an underrun prevention wall that stands on the bottom wall; (c) a first reinforcement side wall that is connected to one end of the underrun prevention wall and one end of the bottom wall; and (d) a second reinforcement side wall that is provided in parallel with the first reinforcement side wall, and that is connected to the other end of the underrun prevention wall and the other end of the bottom wall. In addition, Japanese Patent Application Publication No. 2003-252134 (JP-A-2003-252134) describes an underrun prevention member of which the cross section has an angular U shape or a rounded U shape. The underrun prevention member is disposed so as to straddle an upper end of a rectangular bumper beam, and each of angular U-shaped opening edges is integrally welded to an outer side wall and an inner side wall of the bumper beam.